Global Amphibian Decline and the Fungus Among Us

A recently identified disease called the chytrid fungus Batrachochytrium dendrobatidis has been implicated as the proximate cause of some amphibian population declines in Australia, Central and South America, Europe, and the United States. In the U.S., disease-associated declines have particularly affected the Rocky Mountain boreal toad and the Wyoming toad.

This year, our Wildlife Disease Laboratories developed a rapid molecular test for the fungus that was used in Panama to guide the rescue of hundreds of frogs from the path of the disease just weeks before it arrived.  We continued this critical work by establishing the first zoo-based dedicated chytird fungus diagnostic screening laboratory at the Beckman Center, and banking the first amphibian DNA samples in the Frozen Zoo®. 

This year, the lab provided urgently needed testing of over 2,000 amphibian samples for chytrid fungal infection from field conservation programs, zoo-based survival assurance colonies, and a large survey of wild amphibians in San Diego County in conjunction with the U.S. Geological Survey. 

The Wyoming toad is among the most endangered amphibians worldwide, with approximately 200 animals involved in captive breeding programs and estimates of less than 100 individuals remaining in the wild. Recovery of the Wyoming toad has been hampered by outbreaks of chytrid fungus within the sole remaining wild population and by poor reproductive success and disease issues (chytridiomycosis and vitamin A deficiency) in the captive population.

The Wildlife Disease Laboratories at the San Diego Zoo’s Institute for Conservation Research are supporting the Wyoming Toad Species Survival Plan and the United States Fish and Wildlife Service Toad Recovery Team by providing diagnostic pathology service and advice regarding disease control and prevention, with the goal of minimizing the impact of these conditions on species recovery efforts.

Unique pathology expertise is also provided to biologists studying the role of disease in worldwide amphibian population declines by means of histopathology support for experimental studies and diagnostic evaluation of field samples.

Our significant efforts to help save amphibians were recognized with a major Conservation Leadership Grant award from the Institute of Museum and Library Services.  This award funds a three-year, multi-institutional collaborative effort that makes our unique scientific expertise and laboratory capability available to support the disease control and bioresource banking needs of the amphibian conservation community.